In assessing the efficacy of treatments that affect the skin of a human subject, common techniques have included capturing images of the subject's skin at various points during the course of treatment, and comparing the images. Without such comparisons, the efficacy of skin treatments—whether cosmetic or medical skin care, the application of products, skin care regimens, or skin procedures—is difficult to assess, particularly where the effects are gradual or subtle.
The comparison of images of a subject's skin is complicated, however, when there are significant differences in the images, such as may be due to the lighting conditions in which the images were captured, movement, pose, orientation, and the shape of the area being imaged (such as may be due to treatment, inhalation/exhalation, facial expression, etc.), among other factors.
The comparison of images for assessing the efficacy of skin treatments is further complicated where multiple subjects are involved, as in studies or clinical trials. Such applications typically also demand a high degree of precision and consistency, with objective, quantifiable results.